逆法识别金属板料在颈缩阶段的流动曲线
发布时间：2018-11-26 10:32
【摘要】：有限元方法和计算机辅助仿真分析软件(CAE)广泛应用于汽车研发领域,有助于缩短研发周期和节约研发资金。涉及材料大变形的汽车碰撞安全仿真分析和金属板料成形过程的仿真需要定义材料在大应变处对应的流动曲线,即真应力-应变曲线。材料的应力应变曲线通常使用单向拉伸实验获得,而在实验过程中常用的普通接触式引伸计法无法准确给出材料在大变形阶段的真应力应变曲线。本篇研究内容主要展示了一种逆向识别方法,联合有限元仿真和普通拉伸实验获取金属板料在大变形阶段的流动曲线。主要研究内容包括以下几个方面：(1)钢板是汽车车身常用的金属材料。随着汽车轻量化技术的推广,高强钢和铝合金材料在汽车制造中的使用量越来越大。本文选择低碳钢Q195、铝合金AL6061和高强钢HSLA350三种典型板料作为研究对象。首先按照国标设计并加工标准试样。使用引伸计初步得到三种材料试件的拉伸力-伸长量曲线。经过数据处理后得到工程应力-应变曲线、真应力-应变曲线和真应力-塑性应变曲线。考虑到板料各向异性的影响,沿轧制方向、横向和45°方向截取试件并在拉伸过程中测量厚向异性系数。(2)仿真软件采用的是有良好非线性仿真性能的通用有限元仿真软件ABAQUS(?)。仿真过程中构建了合适的有限元模型,能正确仿真分散性失稳期间的各向异性塑性变形。在验证阶段尝试比较了多种单元尺寸和ABAQUS中包含的单元类型。最终确定的拉伸试件有限元仿真模型包括合理的结构模型、考虑各向异性屈服的材料模型、兼顾仿真精度和效率的单元参数和为了与实验力-伸长量曲线作比较而对应设置的输出项。(3)结合实验与仿真,给出一种逆向识别方法。以实验力-伸长量曲线为标杆,不断外推修正流动曲线直至仿真力-伸长量曲线收敛到实验力-伸长量曲线。最终得出三种板料直至集中性失稳前的全流动曲线。(4)在得出材料完整的直至颈缩阶段的流动应力曲线后,建立多个不同的硬化函数描述该曲线,并比较拟合结果,发现一种改进的Hockett-Sherby函数效果最好并展示了其结果。此外,结合Q195拉伸试件的仿真结果,简要分析了试件在颈缩阶段的应力三轴性行为。
[Abstract]:Finite element method (FEM) and computer aided simulation analysis (CAE) are widely used in the field of automobile research and development, which is helpful to shorten the research and development cycle and save the R & D funds. The simulation analysis of automobile collision safety involving large deformation of materials and the simulation of sheet metal forming process need to define the flow curve corresponding to the material at large strain, that is, the true stress-strain curve. The stress-strain curves of materials are usually obtained by uniaxial tensile tests, but the common contact extensometer can not accurately give the true stress-strain curves of materials in large deformation stage. In this paper, a reverse recognition method, combined with finite element simulation and general tensile experiment, is presented to obtain the flow curves of sheet metal in large deformation stage. The main research contents are as follows: (1) Steel plate is a common metal material used in automobile body. With the popularization of lightweight technology, high-strength steel and aluminum alloy are used more and more in automobile manufacturing. In this paper, three typical sheets of low carbon steel Q195, aluminum alloy AL6061 and high strength steel HSLA350 are selected as research objects. First according to the national standard design and processing of standard samples. The tensile force-elongation curves of three kinds of material specimens were obtained by extensometer. After data processing, engineering stress-strain curves, true stress-strain curves and true stress-plastic strain curves are obtained. Considering the effect of anisotropy of sheet metal, along the rolling direction, The transverse and 45 掳directions are used to intercept the specimen and measure the thickness anisotropy coefficient in the tensile process. (2) the general finite element simulation software ABAQUS (?), which has good nonlinear simulation performance, is used in the simulation software. An appropriate finite element model is constructed to simulate the anisotropic plastic deformation during the dispersion instability. During the verification phase, a variety of cell sizes were attempted to compare with the cell types contained in the ABAQUS. The final finite element simulation model of tensile specimen consists of a reasonable structure model and a material model with anisotropic yield. The element parameters which take into account the accuracy and efficiency of the simulation and the output terms set for comparison with the experimental force-elongation curve are given. (3) combining the experiment and simulation, a reverse recognition method is presented. Taking the experimental force-elongation curve as the benchmark, the flow curve is continuously extrapolated and revised until the simulation force-elongation curve converges to the experimental force-elongation curve. Finally, the total flow curves of three kinds of sheet materials are obtained until the concentrated instability. (4) after the flow stress curves are obtained, several different hardening functions are established to describe the curves, and the fitting results are compared. An improved Hockett-Sherby function is found to work best and the results are shown. In addition, combined with the simulation results of Q195 tensile specimen, the stress triaxial behavior of the specimen at necking stage is analyzed briefly.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U467.14;U466
本文编号：2358320
[Abstract]:Finite element method (FEM) and computer aided simulation analysis (CAE) are widely used in the field of automobile research and development, which is helpful to shorten the research and development cycle and save the R & D funds. The simulation analysis of automobile collision safety involving large deformation of materials and the simulation of sheet metal forming process need to define the flow curve corresponding to the material at large strain, that is, the true stress-strain curve. The stress-strain curves of materials are usually obtained by uniaxial tensile tests, but the common contact extensometer can not accurately give the true stress-strain curves of materials in large deformation stage. In this paper, a reverse recognition method, combined with finite element simulation and general tensile experiment, is presented to obtain the flow curves of sheet metal in large deformation stage. The main research contents are as follows: (1) Steel plate is a common metal material used in automobile body. With the popularization of lightweight technology, high-strength steel and aluminum alloy are used more and more in automobile manufacturing. In this paper, three typical sheets of low carbon steel Q195, aluminum alloy AL6061 and high strength steel HSLA350 are selected as research objects. First according to the national standard design and processing of standard samples. The tensile force-elongation curves of three kinds of material specimens were obtained by extensometer. After data processing, engineering stress-strain curves, true stress-strain curves and true stress-plastic strain curves are obtained. Considering the effect of anisotropy of sheet metal, along the rolling direction, The transverse and 45 掳directions are used to intercept the specimen and measure the thickness anisotropy coefficient in the tensile process. (2) the general finite element simulation software ABAQUS (?), which has good nonlinear simulation performance, is used in the simulation software. An appropriate finite element model is constructed to simulate the anisotropic plastic deformation during the dispersion instability. During the verification phase, a variety of cell sizes were attempted to compare with the cell types contained in the ABAQUS. The final finite element simulation model of tensile specimen consists of a reasonable structure model and a material model with anisotropic yield. The element parameters which take into account the accuracy and efficiency of the simulation and the output terms set for comparison with the experimental force-elongation curve are given. (3) combining the experiment and simulation, a reverse recognition method is presented. Taking the experimental force-elongation curve as the benchmark, the flow curve is continuously extrapolated and revised until the simulation force-elongation curve converges to the experimental force-elongation curve. Finally, the total flow curves of three kinds of sheet materials are obtained until the concentrated instability. (4) after the flow stress curves are obtained, several different hardening functions are established to describe the curves, and the fitting results are compared. An improved Hockett-Sherby function is found to work best and the results are shown. In addition, combined with the simulation results of Q195 tensile specimen, the stress triaxial behavior of the specimen at necking stage is analyzed briefly.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U467.14;U466
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